The present invention relates to a parallel analog device for the local processing of a bidimensional signal. This processed signal can be optical, electrical, acoustic or of some other nature.
In the case where the signal received is a bidimensional optical signal, i.e. an image, the device according to the invention can be advantageously used in numerous fields including medical imaging, robotics (recognition of shapes), videocommunications (compression of information), meteorology, etc. In the case of an acoustic bidimensional signal, the device according to the invention can be used for carrying out processing, such as of an acoustic histogram.
The local processing of a bidimensional signal is carried out by a means receiving, in parallel, a group of component signals organized in accordance with a matrix of p rows and n columns (in which p&gt;1 and n&gt;1) and supplying, in parallel, a group of component signals organized in the same way, where each output component signal is a function of the input component signal of the same rank in the matrix and input component signals in the vicinity of said input component signal.
The function connecting an output component signal to a group of input component signals is called the processing operator which can be linear or non-linear. A window defines the number of input component signals contributing to an output component signal.
In the case where the bidimensional signal is an optical signal, the device makes it possible to carry out processing operations such as smoothing, noise elimination, contrast increase, a detection of contours, patterns or textures, etc.
Throughout the remainder of the text, attention will essentially be directed at devices for the local processing of an image (in the conventional sense it is therefore a bidimensional optical signal). It is obvious that this example is taken for illustration purposes, whereas the invention applies to all such signals, no matter what their nature.
A description will now be given of the main local image processing means according to the prior art. These devices can be classified in two categories, namely digital devices and analog devices.
Local image processing is mainly performed by digital devices. This processing, performed on a conventional computer, is slow because the number of elementary operations is high and approximately 10.sup.6 for a 320.times.320 point image with a 3.times.3 point window. Thus, for example, the local processing of a 512.times.512 point image on a Digital Equipment PDP 11 mini-computer takes approximately 30 seconds calculation.
In order to reach processing speeds compatible with the speed of a video signal supplying 25 images per second in accordance with European standards or 30 images per second in accordance with U.S. and Japanese standards, it is necessary to either use a very powerful computer, or special systems of the parallel processor or systolic machine type. These different systems suffer from the disadvantage of being very complex to realize and program, whilst also being very onerous.
In addition, devices for the analog local processing of an image are know. In principle, these devices require a very high parallelism, because there is a simultaneous processing of all the points of the image. These devices are produced either with the aid of discrete components, or by assembling integrated circuits each processing about 100 image points. Thus, these devices cannot be used for processing normal sized images, i.e. having at least 10.sup.5 image points, due to the number of discrete components or the number of integrated circuits which would be necessary, the complexity of their assembly and their cost.